High frequency generator



March 28, 1939. E. HABANN ET AL FREQUENCY GENERATOR Filed Aug. 22, 1956 [in anion M/70km Patented Mar. 28, 1939 UNITED sTATEs PATENT on-10 2,151,912 HIGH FREQUENCY GENERATOR Application August zz, i936, SerlaLNo. 97,394

In Germany August 24, 1935 7 Claims.

The invention relates to arrangements for producing high frequency oscillations by means of electron tubes of thekind having a split anode, that IS, an anode made in two or more parts disposed in cylindrical relation to the glowing cathode or filament. Tubes or valves of this type have a magnetic field arranged to act along the axis of the anode and thus along the filament.

The invention has for its object to improve the mode of operating oscillation generators of this kind and in thisconnectionalso to improve the construction thereof, and will be understood from the following description, reference being had to the accompanying drawing in which Fig. 1 is a partially perspective and partially sectioned diagrammatic view of an example of the novel arrangement. Fig. 2 shows a section on the line 22 of Fig. 3, Fig. 3 a section on line-3-3 of Fig. 2, both Figs. 2 and 3 disclosing improvements upon the arrangement illustrated in Fig. 1. Fig. 4, drawn to a larger scale than Figs. 1 to 3, shows a section through one of the conductors of the oscillatory circuit or Lecher wire system of the electron tube and relates to an improvement upon these conductors as represented in Figs. 1 to 3.

The electron tube 1 has an anode that consists of two cylinder portions 2. The cathode 9r filament 3 thereof is disposed in the axis ofthe cylinder 2, 2. A source of current 4 serves to heat the filament 3. The magnetic field acting along filament 3 is that of an electro-magnet 5. Connectedinseries with the current source 6 for magnet 5 is a variable resistance 1. To the anode parts 2 are fastened two metallic sheets 8 which are interconnected by a bridge 9 adapted to bedisplaced between them. The arrangement 8, 9 is the oscillatory circuit or Lecher wire system of the tube l. The anode voltage is supplied by a-current source I0 which is connected to the middle of the bridge 9 in the manner. represented and is connected also to filament 3 over a variable resistance ll.

Tube 1 and Lecher wire system 8, 9 may be contained in, a casing l2, as shown in Figs. 2' and 3. Casing l2 may .have openings l 3 opposite each other in order that air may be moved through thecasing by a fan or blower M, as indicated by the arrows in Fig. 3, the object being to cool the sheets 8. These may be provided with ribs l5 and may also consist of a core l5 and coatings l1 thereon, as illustrated in Fig. 11.

v The means described herebefore may be employed-either individually or conjointly and' serve as negative resistance for the oscillatory circuit or Lecher wire system for a purpose stated hereinafter.

The frequency of the oscillations'generated by devices of this kind is determined substantially by the tuning system, the anode potential, the radius of the anode cylinder and the strength of the magnetic field. These oscillations are defined by the formula a-"2F ,where H is the magnetic fieldstrength in gauss,

the ratio of the charge of an electron to the mass thereof, Va the anode potential and Ta the radius of the anode cylinder.

The fieldstrength defined. by this formula is that oscillations can arise with values of the field strength which are either below or above this critical value.

In addition to the fieldstrength defined by the Formula I there is still another critical fieldstrength, this being defined by the formula 10650 A cm.

designated as the critical one. It is well known where the magnetic fieldstrength H is expressed in gauss and the wavelength A in centimetres. This second field strength defines a rotational move ment of the electrons with a certain rotational frequency within the discharging space in their cycloid-shaped course with a certain rotational frequency corresponding to the number of the rotational movements effected by the electron under the influence of the magnetic field strength.

The rotational frequency of the electrons is independent of the speed of the electrons caused by the anode voltage and exists already at the start speed, supplied to the electrons by the heat movement at the emission. In case the rotational frequency is equal to the natural frequency of the connected oscillatory circuitno oscillations will occur therein. This refers to the frequency range .of the generated oscillations, wherein the tube is used as negative resistance for the oscillation generation. If, for example, witlia frequency of 3.10 kilocycles a wavelength of 10 metres is generated then about gauss are required. The rotational frequency in this case. is 3.10 kilocycles.

It has now been found that far below this critical value of the magnetic fieldstrength, i. e. the value defined by the two Formulae I and -]I,- that is to say with a relatively low anode potential; oscillations occur which have not been known so far. It has been experienced that there is a certain range of fieldstrength in which no oscillations arise under ordinary circum stances, whilst predetermined conditions will cause special oscillations to originate and these are obtained only if the oscillatory circuit is to a high degree free of'attenuation.

This novel range involves a great advantage inasmuch as it admits of reducing the voltages and magnetic fieldstrengths, which even in the case of short waves are extrenqely high, to such extent that devices of this kind need not be given dimensions so small that the devices are difficult to handle. For instance, larger tube diametres may be employed in cases that otherwise require extremely small diametres to be employed. The;

rotational frequency is other than the produced frequency, being greater than this. If the magnetic fieldstrength is' reduced to a small value so that the rotational frequency will be in the neighbourhood of the produced frequency, this frequencynbeing determined by the oscillating circuit of the tubithen theoscillations will cease after having decreased quickly in energy. It is not possible to generate oscillations within a range in which the rotational frequency and the frequency to be generated accord with. each other.

The invention is based on the supposition that 4 the rotational frequency should not be considered a commencement as regards frequencies which may perhaps be obtainable, but that the rotational frequency only forms a gap in the range of oscillations. with smaller fieldstrengths oscillations will originate again, namely oscillations of a frequency higher than is the rotational frequency. Such oscillations however only arise if the attenuation of the oscillating circuit of the tube is extremely small.

In order that this oscillatory circuit be sufliciently free of attenuation, with a view to making accessible said range, the sheets 8 are attached to the anode members 2 in the manner before described, so as to take the place of the customary Lecher wires. Also, for diminishing the attenuatiorrpf the oscillation circuit it is suitable to cool the sheets 8 so as to avoid a rise in the temperature thereof caused by the cur-- rents. For instance, the sheets may be acted upon by an air current produced by the fan or blower I! in the manner before stated. The described ribs l5 will assist the air current in its cooling action. Instead of the fan [4 any other suitable device may serve to produce the air current for cooling. Further, the cooling action is aided by a certain thickness of the sheets 8 and also by the provision of thecoatings I! as described with reference to Fig. 4, these coatingsconsisting of a metalof high electric conducticity,. such as silver. In this case also the thermal conductivity is very great so that any heat will be quickly led away. Finally, attenuation effects may be obviated by avoiding radiation as far as possible. ,In order to perform this a-casing such as I2 may be provided.

It is'to be understood that these embodiments of the invention may be modified without departing from the spirit of the invention. For instance, the anode of the tubel may consist of more than two parts, for example of four parts, and any cooling means other than these described may be used.

What is claimed is:

1. In an arrangement for generating high frequency oscillations, an electron tube having a split anode, a cathode symmetrically surrounded by said anode, an oscillation circuit connected with said electrodes, means to produce along said cathode a magnetic field whose intensity expressed in gausses is below the value A cm.

- wherein X is the wave-length, and by which value the rotational frequency of the electrons is determined, means to decrease the anode potential to such a low value that the rotational frequency of the electrons will be less than the frequency of said oscillation circuit, and means for reducing the attenuation of said circuit to such an extent that oscillations will be produced which will be of higher frequency than those that would be produced by adjusting said field intensity of the tube to a value higher than said value A cm.

the circuit being tuned to said higher frequency.

'2. An arrangement according to claim 1 s 5.,.An arrangement according to claim 1 wherein said means for reducing the attenua- 'tlon comprises metallic sheets. constituting the conductors of said oscillation circuit, and means for producing air currents to cool said sheets.

6. An arrangement according to claim '1 wherein said means for reducing the attenuation comprises metallic sheetsv constituting the conductors of said oscillation circuit, and a coating of very great electrical conductivity ,gn said sheets.

'7. An arrangement according and in which said means comprises metallic sheets constituting the conductors of said oscillation circuit, and a coating of silver on said metallic sheets. I

,ERICH HABANN.

FELIX GERTH.

to claim 1" 

